Good engineers find the actual maximum pressure before explosion (such as by proof testing, other methods used in other disciplines such as power electronics) or by re-using other well-proven limits if they apply, then warn the customer to stay within a safe limit, usually ⅓ to ¼ the maximum limit. It allows emergencies to be managed and for mishaps to not be harmful to the maximum degree. As well, the combination of rim/tire/spoking/hub is a system, not just a pile of individual parts, and it gives safe behavior because its used within the limits of the interaction bstween the system elements, not only the failure of one part. Why do we stress-relieve spokes? Why do we roll the just-mounted wheel to help the bead/inner tube to interface correctly?